The sport cannot afford to engage in a witch hunt for the name of every player who abused drugs in hopes of gaining a competitive advantage, Mr. Mitchell said. Instead, it should focus on measures that can control or solve the problem for the future.

"Being chained to the past is not helpful," Mitchell told panel members.

Mitchell drew an analogy with his experience as a mediator in Northern Ireland. In that situation, the release of political prisoners was a necessary step toward reconciliation, though it was a painful and difficult step at the time.

The Mitchell report contained numerous recommendations for action, including the implementation of a tougher testing program, greater reliance on other evidence such as canceled checks and known drug dealer testimony, and independent direction of the antidrug effort.

Mitchell said the Major League Baseball commissioner's office and the player's union have begun discussions about the adoption of some of these steps.

But he noted that both sides have large constituencies to which they must answer: 30 team owners on the part of the commission, and 1,200 athletes on the part of the union.

Individual players are still clearly in danger of prosecution or punishment due to their past actions, however. At the beginning of the hearing panel chairman Rep. Henry Waxman (D) of California announced that he has asked the Justice Department to investigate whether former American League Most Valuable Player Miguel Tejada lied to committee staffers when he denied using steroids in a 2005 interview.

For his part, commissioner Bud Selig said he fully supported the Mitchell Report suggestions, and had already moved to adopt those he could unilaterally adopt. And players union chief Donald Fehr admitted that he has come to see that baseball's problem with performance-enhancing substances is larger than he at first had realized.

"The player's association accepts its share of responsibility for what happened ... And so do I," said Mr. Fehr.